1. Field of the Invention
The present invention is directed, generally, toward shipping and handling of perishable goods. More specifically, the present invention is directed toward a mobile container which facilitates the economic shipping and ripening of perishable goods such as produce, including fruits and vegetables, and especially such perishable goods which may become climacteric as they undergo an exothermic ripening process.
2. Description of the Related Art
Refrigerated vehicles have long been employed in a wide variety of applications including the storing and marketing of perishable commodities, particularly produce such as fruits and vegetables, as well as other perishable foods including processed and frozen or chilled products such as ice cream, yeast, etc. The refrigerated vehicles contemplated by the present invention include, for example, truck trailers for road transport and piggy-back use, railroad cars and container bodies contemplated for land and sea service, and the like. Accordingly, all refrigerated containers of the type referred to above are included within the present invention under the general designation of refrigerated containers or vehicles adapted to receive cargo in a refrigerated space.
Shipping and handling of produce which undergo an exothermic ripening process presents certain problems which must be effectively addressed to avoid spoiling the produce. For example, this exothermic ripening process can generate a considerable amount of heat. The temperature of the produce must be accurately controlled to control the ripening process or to delay the ripening process until the produce may be brought to or near the ultimate consumer. Such accurate control of the produce prevents uneven ripening, premature spoilage and other problems. Produce of this type may include fruits such as bananas, tomatoes, avocados, melons, pears, honeydews, and the like.
More specifically, it has long been known that ripening bananas give off or produce a tremendous amount of heat. Thus, the shipping and handling of bananas has been the subject of considerable study directed toward the problem of prohibiting the onset of the ripening process during shipping, controlling the ripening process once it has begun and the delivery of semi-ripened or ripened bananas to retail outlets such as grocery stores and the like with a minimum amount of spoilage. The onset of the ripening process for bananas is a function of temperature. Once the ripening process has begun, the speed of this process is a function of time and temperature--both of which must be delicately balanced to produce favorable results. Other fruits and vegetables undergo similar exothermic ripening processes. However, since bananas enjoy particular popularity among the consuming public, not only in the United States but in a majority of the populated world, and because transporting bananas presents some of the most difficult problems in terms of controlling the ripening process, for purposes of the discussion that follows, it will be assumed that the produce in question are bananas. However, it will be appreciated that the present invention may be employed with other types of perishable goods.
Boxes of produce are sometimes transported from packing facilities to ships in non-air conditioned trucks or railroad cars. Alternatively, the fresh-picked produce may be immediately chilled to reduce the temperature of the goods in a container conventionally known in the art as a "pre-cooler." This is done to preserve the quality and freshness of the fruit. Bananas are typically shipped from their country of origin packed in ventilated, corrugated cardboard boxes on pallets. The fruit is wrapped in plastic liners that have small openings throughout the plastic liners. The typical banana box, for instance, is 10" high, 16" wide and about 20" long and is stacked on a pallet eight boxes high with six boxes to a layer.
When the palletized fruit leaves the country of origin, it is usually loaded onto refrigerated ocean going ships. On the ships, the fruit is either containerized or "break bulked" and later off-loaded to mobile containers for overland transportation to warehouses or ripening facilities. This journey by ship can last anywhere from three to five days, depending on the country of origin. During this time, the bananas are held at a pulp temperature of 56.degree. to 58.degree.. At these temperatures, the bananas will not begin to ripen absent inducement by artificial means as will be discussed below. Upon discharge from a ship, the break bulked fruit or refrigerated containers may be transferred to trucks or chassis for delivery to ripening facilities, customers or processors. Alternatively, the fruit may be transferred from the containers into air conditioned trucks or air conditioned railroad cars for transportation to ripening facilities, customers, or processors. The temperature in the refrigerated trucks is typically set at 57.degree. in the warm months of the year and 60.degree. in the colder months. Due to extreme cold during the winter in some regions of the United States, the side walls and corners of the trailers run cooler. In harsh winter conditions, the bananas are susceptible to chill. Therefore, the refrigerated trucks are run warmer in the winter than in summer months. In the trucks and other similar containers, the conditioned air is Generally supplied from a unit at the front of the container and is blown across the top of the cargo to the back of the container. However, the air is not pressurized to any significant extent. Some trucks are provided with slotted floors which facilitate access of air to the bottom of the boxes.
At processing facilities, the banana boxes are placed in specially designed ripening rooms provided with insulated, gas tight walls and roof panels. The rooms are generally 30 to 40 feet long and 10 to 15 feet wide and have heights accommodating stacks of boxes in racks of two or three tiers or stacks of boxes in tiers without racks. Each room contains an air handling unit which cools or warms the air. Large fans are employed to circulate the air around the room under pressure. The temperature of the air in these ripening rooms is controlled in accordance with a ripening schedule, and ethylene gas is dispersed in the room at predetermined times to facilitate uniform ripening of the fruit. In the case of bananas, for example, the fruit is held in the ripening rooms for four or five days before the fruit is sufficiently ripe. When originally placed in the ripening rooms, not all hands in a box of bananas have the same maturity. Ethylene gas promotes even ripening in bananas at the lowest possible temperatures in a minimum amount of time. It enables all the fruit in one ripening room to turn out evenly. Ethylene is a natural by-product of bananas. The fruit may be gassed in a room for approximately 24 hours where it is exposed to ethylene at a rate of 100 to 300 parts per million. The gas is used to bring all of the fruit to the same 10 to 15 parts per million of ethylene. From the ripening room, the semi-ripened or ripe palletized fruit is then returned to a mobile, refrigerated trailer for transportation to another distribution center or retail outlet.
Ripening rooms are expensive to build and maintain. They are large and take up a considerable amount of space. In fact, ripening rooms are designed with a view toward the conventional wisdom that a large volume of free space in any ripening room is required in order to dissipate the heat emitted from the ripening fruit. They also have fixed capacities. Thus, any method or apparatus which can effectively shorten the time for ripening the fruit without sacrificing quality will increase the capacity of the ripening facility and thereby reduce costs and increase profits.
In the past, it has been suggested to employ the mobile trailer or shipping container for a portion of this ripening process. By starting the ripening process in the trailer or shipping container two or three days before the fruit reaches the ripening center, the processing time required in the larger ripening rooms may be reduced by half or more thus increasing productivity of the ripening facility. There are a number of devices which have been disclosed in the related art which, on their face, purport to accomplish this objective. However, none of the devices known in the related art have been implemented commercially to date because of certain problems which have heretofore been insurmountable.
The typical refrigerated mobile trailer or shipping container used to transport perishable goods is not adequate to handle the inherent temperature rise caused by the exothermic ripening process which bananas and other climacteric fruit undergo. More specifically, bananas go through a continuing process of respiration depending on maturity and pulp temperatures. They take in oxygen and give off carbon dioxide, ethylene gas and other volatile esters. Several changes occur during the respiration process. Starch converts to sugar and the hard pulp softens. The green chlorophyll of the peel is destroyed allowing the yellow carotene to show through. In addition, the bananas generate an extreme amount of heat. During this build up and particularly at maximum heat production, accurate pulp temperature control is essential. In short, the great heat output of the ripening process is more than any currently known refrigerated container in commercial use is capable of dissipating. In mobile trailers and shipping containers, the banana boxes are stacked close to the ceilings to preserve and maintain economical transportation costs. When the ripening process was initiated in such containers in the past, the temperature in the container would typically rise inordinately in an uncontrolled way such that the ripening process was escalated and ultimately led to the deterioration of the fruit. The heat generated by the exothermic ripening reaction is simply far beyond the capacity of the refrigeration and fan means on trailers or shipping containers conventionally used to deliver cooled air in sufficient quantities to uniformly absorb and reject the heat generated during this process. Attempts in the past to employ trailers modified to address this issue have resulted in limited cargo space which accommodates only small loads or have resulted in damaged fruit that is ultimately unsaleable. Thus, the modified containers proposed in the past are simply not economically viable and for the most part have not been employed to ripen fruit to any commercially recognizable extent.
In contrast, ripening rooms have a much larger volume than mobile shipping trailers as well as much higher cooling capacities. Thus, the ripening room is capable of handling the exothermic ripening reaction produced in climacteric fruit. Examples of ripening rooms conventionally known in the art include those disclosed in U.S. Pat. No. 5,531,158 issued to Perriman, Jr. on Jul. 2, 1996 for a produce ripening apparatus and method, as well as U.S. Pat. No. 5,566,608 issued to Vejdani et al. on Oct. 22, 1996 for a vertical flow ripening room. However, the physical structure, components and technology employed in ripening rooms to handle the heat generated during the banana ripening process is simply not compatible with mobile containers--especially those which are towable behind a truck over roads, highways and the like. Accordingly, the devices disclosed in the above-identified patents as well as similar, related art, are simply non-analogous to the present invention.
Thus, there remains a need in the art for a mobile refrigerated container with sufficient air flow and cooling capacity to adequately control the climacteric fruit during its exothermic ripening process. In addition, there is a need in the art for such a mobile container with an economically sufficient capacity for hauling the fruit so that shipping the fruit in this way remains cost-effective and competitive. Furthermore, there remains a need in the art for a mobile container of this type which is also suitable in size and capacity for shipping goods other than ripening fruit so that the trailer may be effectively employed during back hauls to the initial shipping point or anywhere else.